The present invention relates to a device for removing air from hermetically sealed, automatically emptying centrifuge drums in which a rotating drum space is connected to and sealed off from non-moving supply and removal lines by mechanical seals and in which there is an air-removal valve in the supply line for removing air from the drum space.
A device of this type for removing air from hermetically sealed, automatically emptying centrifuge drums is known. It has an air-removal valve in the supply line that communicates through a tube with the space inside the centrifuge drum. German Pat. No. 470 723, for example, discloses a device of this type in a hermetically, completely jacketed centrifuge.
Air must be pumped out of the space inside the hermetically sealed centrifuge drum in a system of this type before it can be charged with liquid. Although some of the air in the drum can, of course, escape directly over the removal line of the centrifuge, the liquid will form a seal between the center of the drum and the solids space as the centrifuge is being filled, leaving a bubble of air in the center. The centrifuge can not be operated unless this bubble can be removed because there will not be enough of a pressure difference between the intake and the outlet unless the center of the drum is completely full of liquid.
Air is removed manually from the space inside the drum through an air-removal valve in the supply line of known hermetically sealed centrifuges, and, since the air-removal tube that communicates with the valve is located near the incoming liquid, liquid can not be prevented from escaping as well while the air is being removed.
Whereas air must be removed from the hermetically sealed, completely jacketed centrifuge disclosed in German Pat. No. 470 723 only once before the commencement of each separation, it must be removed after each emptying in the hermetically sealed, automatically emptying centrifuges preferably employed at the present time. Since such centrifuges are mostly emptied automatically by appropriate controls, the possibility of automating the air removal as well is desirable. The application of an automatic valve to replace the manual controls has been attempted. Such a valve would open for a specific amount of time subsequent to emptying. Since, however, the amount of air entering the drum can vary considerably, it will either not get removed entirely or some of the product will get lost because the valve remains open too long. Furthermore, since the air-removal tube has to be narrow, it takes a relatively long time to remove the air.
Although removing the air from the drum with commercially available air removers that incorporate a float valve and are mounted in the supply line of the centrifuge has accordingly been attempted, it turns out that, if a product tends to foam, the foam will also escape constantly from the air remover because foam, as it rises will not seal off a float valve. Furthermore, known air removers do not prevent oxygen from entering, and this is undesirable in many products. Nor can such air removers be cleaned thoroughly enough automatically.